Two piece lens grinding lap

ABSTRACT

A two piece grinding lap comprising a lens surfacing member and a body member. The lens surfacing member includes depending lugs adapted to be received in corresponding detents in the body member and may be made of a non-ferrous material such as plastic. Both grinding and polishing can be carried out by using either a grinding pad or a polishing pad on the curved surface.

United States Patent 1151 3,685,214 Sarofeen [451 Aug. 22, 1972 [54] TWO PIECE LENS GRINDING LAP 1,487,024 3/ 1924 Robinson ..5 1/209 DL 72 In G e M Sal-0f C l 2,932,138 4/1960 Fluskey ..5l/209R 1 van Heigl ns, Va. J 1,202,235 10/1916 Stead ..51/209 DL 3,128,580 4/1964 Davis ..51/209 R X 1 Asslgnw Vaerco, (301011181 fights, 2,441,472 5/1948 DAvaucourt ..51/216 LP [22] Filed: Oct. 12, 1970 Primary Examiner-Donald G. Kelly [21] 79,978 Att0rneyCameron, Kerkam & Sutton [52] US. Cl ..51/209 DL ABSTRACT [51] Int. Cl. ..-B24d 17/00 A two 1 plece gnnding lap comprlsmg a lens surfacmg [58] held of "''ig'fiy gff g 22 member and a body member. The lens surfacing I 'member includes depending lugs adapted to be received in corresponding detents in the body member [56] References C'ted and may be made of a non-ferrous material such as UNITED STATES PATENTS plastic. Both grinding and polishing can be carried out by usmg e1ther a grlndmg pad or a pollshmg pad on 3,522,680 8/1970 Sarofeen ..51/358 the curved Surface 1,672,574 6/1928 Maynard ..51/209 DL 8 Claim, 8 Drawing Figures PATENTEH B I 3.685.214

sum 2 or 2 IRVEHTOI! GEORGE M. J- SAROFEEN ATTORNEYS TWO PIECE LENS GRINDING LAP This invention relates to improvements in abrading apparatus and has particular reference to the provision of a two piece grinding lap which permits rapid changing of lens surfacing members.

In general, prescriptive curvatures are applied to ophthalmic lens blanks by rough grinding or generating to the approximate desired curvature on a particular side of the lens blank. Following the rough grinding step, the ground side is further ground to a precise curvature. Thereafter, the fine ground side is polished to a high degree of optical perfection.

The fine grinding or fining operation is commonly accomplished by placing the surface of the lens blank in contact with a cast iron lap or surfacing tool having a predetermined surface curvature thereon which is precisely formed to the desired curvature to be reproduced. A slurry containing abrasive particles of a selected size to the tool surface is applied while introducing a controlled pressure and oscillatory motion to either or both the tool and lens blank so as to cause the abrasive particles to abrade the surface of the blank. In this manner, the lens surface eventually assumes the shape of the surface of the lap or surfacing tool.

The abrasive action of the slurry during the operation, causes the preformed cast iron surface of the tool to wear away. Eventually, enough wear takes place to introduce errors of curvature to the tool surface generated thereby. For this reason, it has been necessary to carefully gauge the curvature of the abrading surface of the tool before each fining operation. When an excessive amount of wear has taken place, the abrading surface must be renewed by a well known, but costly truing operation. On the average, the tool must be trued after each three or four grinding operations.

Eventually, the tool can no longer be trued and must be replaced.

When a curve change is indicated, in order to true the surface, the tool must be removed from its mounting. Generally, the tool is mounted to a rotary drive shaft which is tapered at its free end and which fits into a correspondingly tapered recess, and when a curve change is indicated, it is necessary to break the tapered fit between the end of the drive shaft and the tool. In view of the criticality of dimensions in the fining or polishing process, the fit is extremely tight and requires a sizable amount of effort to effect separation of the parts. Obviously, this step is time consuming and breaks the rhythm of the work pattern of the operator. Because of the frequency of the truing operation, the frequent removal of a surfacing tool affects overall production costs to a considerable degree.

The present invention is intended to overcome the above-mentioned difficulties and disadvantages and other limitations inherent in present day lens surfacing techniques through the provision of a novel two piece grinding lap which allows the use of non-ferrous materials to support the abrading surface of the lens surfacing tool and which permits rapid changing of the lap curvature when a curve change is required either due to wear of the surface or a change in the desired prescriptive curvature.

Another object of the present invention is to provide an inexpensive, quickly replaceable lens surfacing tool.

A further object of the invention is to provide a detachable lens surfacing member for a lens surfacing tool.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a fragmentary elevational view, partly in cross section, showing a conventional blocking device having a lens blank affixed thereto and applied to a surfacing tool to form a prescription curve thereon;

FIG. 2 is a perspective view of the lower body member of the two piece grinding lap of the present invention;

FIG. 3A is an elevational view of the lens surfacing member of the two piece grinding lap of the present invention;

FIG. 3B is a bottom view of the lens surfacing member shown in FIG. 3A;

FIG. 4 is an assembly view of the two piece grinding lap with the lens surfacing member being capped on the body member;

FIG. 5A is a perspective view of the lower body member or holder of an alternate embodiment of a two piece grinding lap, while FIG. 5B is a perspective view of the cap or lens surface of the two piece grinding lap of the present invention; the cap being adapted to be received within the holder when the pieces are assembled; and

FIG. 6 is a perspective view of an alternate embodiment of a lower body member or holder for the two piece grinding lap of the present invention.

Referring more particularly to the drawings in which like reference characters represent like parts throughout the several views thereof, the device embodying the invention comprises a grinding lap 10 having a body member 11 and a lens surfacing member 12 formed of cast iron or other suitable shape retaining material. Preferably, the lens surfacing portion is made of a non-ferrous material and has applied thereto a suitable wear surface 13 bonded to the lens surfacing member by a thin layer of adhesive 14.

A preferred form of wear surface is an expanded metal facing of the type shown and described in my aforementioned US. Pat. No. 3,522,688. Such facings are sheet-like in form and provided on one side thereof with a thin layer of adhesive. The outer side of the adhesive layer is provided with a removable protective latex strip or sheet or some other suitable treated layer of paper cloth or the like. The strip is adapted to be removed or stripped just prior to securing the facing to the non-ferrous surfacing portion. It should be readily apparent that although the curved surface of the surfacing portion of the grinding lap is illustrated as being convex, the facing may be made to conform to and be applied to concave tool surfaces. Also, the replaceable facing may be of other types, such as, for example, the type disclosed in U.S'. Pat. No. 2,886,923. Of course, where a polishing step is being performed, the lens surfacing member has applied thereto a polishing pad.

Referring to FIG. 1, the tool 10 is generally secured to a driving spindle 16 adapted to be rotatably driven by a drive motor (not shown) of a conventional lens surfacing machine 17. To this end, body member 11 is provided with a tapered bore 18 which enables the body member 11 to be press fitted to the correspondingly tapered end of the drive spindle. A lens blank 19 having been previously attached to a holder 20, is positioned upon the expanded metal facing 13 of the tool. An oscillating or rotating motion is then imparted in a well known manner to the drive spindle 16 while the attached lens blank 19, through suitable alignment retaining means 21 and crank spindle 22, simultaneously describes a path of movement relative to that of the tool 10. The combined movement between the lens blank 19 and facing 13 then produces a scrubbing action on the surface of the blank. An abrasive slurry 23 is applied to the facing 13 between the facing and the lens blank. Due to the scrubbing action, the surface of the blank is abraded to a point where it assumes precisely the shape of the abrading face of the facing.

As hereinbefore pointed out, in such operations, frequently it is necessary to remove the surfacing tool to true the tool surface back to its initial curvature or to substitute a tool having a different prescriptive curvature. In accordance with the present invention, this operation is made simply and efficiently with a minimum of effort and disruption of the lens fabricating process.

To this end, as most clearly shown in FIGS. 2-4, the grinding lap of the present invention is made of two pieces, a body member 11 and a readily detachable lens surfacing member 12 which in its assembled position forms a cap on the body member. Body member 11 may be of a cupped configuration having a centrally located, downwardly depending shank 24. The tapered bore 18 is located within the shank for the purpose of mounting the body member to the drive spindle 16 of a grinding, fining or polishing machine as hereinbefore described.

The upper portion of the cupped body member includes an annular rim 25 having a plurality of detents or channel or slot-like grooves 26-29 adapted to cooperatively receive lugs 30-33 formed in a projecting rim 34 on the lens surfacing member 12. When positioned in the grooves, the lugs serve to restrain the member 12 from movement relative to the body member as the tool is rotatably driven or oscillated. In the preferred arrangement four detents are provided. However, more or less may be utilized, so long as the cap is snugly received about the body member and is not subject to relative movement with respect thereto while the spindle is driven.

The construction of the body member 12, most clearly shown in FIGS. 3A and 33, includes an annular projecting rim 34 which depends from the curved surface 15 of the lens surfacing member. The inner diameter of rim 34 is slightly larger than the outer diameter of rim 25, while the dimensions of the lugs are such that they are snugly received in the corresponding detents. Lugs 30-33 form cross-ribs within the rim 34 of the surfacing member to add greater rigidity to the structure. Preferably, the lens surfacing member is fabricated from a non-ferrous material such as, for example, plastic. The plastic member may be molded so that the curved surface 15 corresponds to a desired prescriptive curvature.

When a curve change is indicated, it is only necessary to raise the cap or lens surfacing member 12 from the body member 11. This requires only a slight effort. After removal of the cap, the member 12 is replaced with another cap of desired curvature. Obviously, because of the economy of construction, many surfacing members of the same prescriptive curvature may be prefabricated and ready for use so that the heretofore required truing of cast iron pieces is obviated. However, where the caps are of a cast iron construction, the truing may be performed at the operators leisure by another, since the rapid detachment and replacement of lens surfacing members enables the continuous grinding of the lens in almost an uninterrupted process.

FIGS. 5A and 5B illustrate another embodiment of the present invention wherein the lens surfacing member or grinding cap 12 advantageously includes a projecting rim that extends downwardly, as viewed in the drawing, to fit within the holder or body member 11. Body member 11 is substantially cylindrical in shape and forms a pedestal on shank 24. The upper surface of the body member is milled or otherwise cut away to form four pie-shaped upwardly extending spaced segments or lugs 35-38. If the holder and cap are fabricated from a non-ferrous or plastic material, the parts may be conveniently molded to shape. The four segments are spaced from each other by intersecting grooves or channels 39 and 40. The outer curved sides of the pie-shaped segments are spaced inwardly from the perimeter of the body member to provide an annular surface or ledge 41 surrounding the segments. The outer peripheral surface of the,body member has secured thereto an upwardly annular rim 42 which forms an annular channel between the inner surface of the rim 42 and the outer curved surfaces of the pieshaped segments.

When the grinding cap 12 and corresponding holder 11 are assembled, the annular projecting rim 34 on the grinding cap is positioned in a snug fit within the holder. Lugs 30-33 form intersecting cross pieces within the rim and fit within the intersecting channels 39 and 40, while the annular rim portion 34 is received within the annular channel of the holder formed between rim 42 and segments 35-38. The segments 35-38 are adapted to have a snug fit in correspondingly shaped openings in the cap. While segments 35-38 are illustrated as being pie-shape, other forms may be utilized, in which case the openings in the cap within which the segments are received are correspondingly shaped to provide the snug fit.

Further stability is gained by providing in the lens surfacing cap member an outer annular channel 44 surrounding the rim 34. Channel 44 extends into the grinding cap so as to be capable of receiving rim 42 when the cap and holder are assembled. The outer portion of the cap thus forms a second projecting rim 45 which surrounds rim 42 when the cap and holder are joined in their operative position.

FIG. 6 illustrates a variation of the holder. As illustrated, the curved surfaces of the segments 35-38 extend to the outer peripheral edge of the body member. Such a construction avoids the necessity of providing an annular channel 44 and rim 45 and provides a simplified construction that affords a considerable economy in the manufacture of the cap and holder.

It will be apparent that many modifications will suggest themselves to those skilled in the art as to the details of construction and arrangement of parts shown and described without departing from the scope of the invention as expressed in the accompanying claims. Therefore, it is to be understood that all the material set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A lens grinding lap comprising a body member, said body member being adapted to be connected to a drive source for rotatably driving or oscillating said lap, a detachable lens surfacing cap member adapted to be received over said body member, said cap member having a prescribed surface portion for generating a lens blank to a corresponding curvature, first means on said body member for restraining said cap member from relative movement with respect thereto and second means on said cap member cooperating with said first means to effect said restraint, said first means comprising a plurality of detents and said second means comprising a plurality of lugs adapted to be received by said detents, said lugs forming cross-ribs within said cap member.

2. A lens grinding lap as set forth in claim 1 wherein said cap member is of a non-ferrous material.

3. A lens grinding lap as set forth in claim 1 wherein said cap member is of a plastic material.

4. A lens grinding lap comprising a body member, said body member being adapted to be connected to a drive source for rotatably driving or oscillating said lap, a detachable lens surfacing cap member including means adapted to be received within said body member for maintaining said body member and cap member in assembled relationship and said cap member having a prescribed surface portion for generating a lens blank to a corresponding curvature, said means within said body member including an annular rim, intersecting cross pieces within and connected to said annular rim, said body member including cross channels adapted to receive said cross pieces and an annular channel adapted to receive said annular rim.

5. A lens grinding lap as set forth in claim 1 wherein said body member is of a cupped configuration having an annular rim, said detents being formed on said rim to provide a plurality of slot-like grooves, said cap member including a depending annular rim adapted to be fitted over the rim of said body member said lugs adapted to be cooperatively received in said slot-like grooves so as to restrain said cap member from relative movement with respect to said body member, but permitting detachment of said cap member from said body member.

6. A lens grinding lap as set forth in claim 1 further including a wear surface bonded to the prescribed surface portion.

7. A lens grinding lap as set forth in claim 4 wherein said cap member is of a non-ferrous material.

8. A lens grinding lap as set forth in claim 4 wherein said cap member further includes an annular channel about said rim and said body member further includes a rim adjacent said annular channel and adapted to be received within said last named channel.

" UNITED STATES PATENT OFFICE 569 CERTIFICATE OF CORRECTION Patent No. Dated a t 22 1212 I Inventor(s) George M. J. Sarofeen,

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 46, "3,522,688" should be -3,522,680--.

Signed and sealed this 23rd day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. A lens grinding lap comprising a body member, said body member being adapted to be connected to a drive source for rotatably driving or oscillating said lap, a detachable lens surfacing cap member adapted to be received over said body member, said cap member having a prescribed surface portion for generating a lens blank to a corresponding curvature, first means on said body member for restraining said cap member from relative movement with respect thereto and second means on said cap member cooperating with said first means to effect said restraint, said first means comprising a plurality of detents and said second means comprising a plurality of lugs adapted to be received by said detents, said lugs forming cross-ribs within said cap member.
 2. A lens grinding lap as set forth in claim 1 wherein said cap member is of a non-ferrous material.
 3. A lens grinding lap as set forth in claim 1 wherein said cap member is of a plastic material.
 4. A lens grinding lap comprising a body member, said body member being adapted to be connected to a drive source for rotatably driving or oscillating said lap, a detachable lens surfacing cap member including means adapted to be received within said body member for maintaining said body member and cap member in assembled relationship and said cap member having a prescribed surface portion for generating a lens blank to a corresponding curvature, said means within said body member including an annular rim, intersecting cross pieces Within and connected to said annular rim, said body member including cross channels adapted to receive said cross pieces and an annular channel adapted to receive said annular rim.
 5. A lens grinding lap as set forth in claim 1 wherein said body member is of a cupped configuration having an annular rim, said detents being formed on said rim to provide a plurality of slot-like grooves, said cap member including a depending annular rim adapted to be fitted over the rim of said body member said lugs adapted to be cooperatively received in said slot-like grooves so as to restrain said cap member from relative movement with respect to said body member, but permitting detachment of said cap member from said body member.
 6. A lens grinding lap as set forth in claim 1 further including a wear surface bonded to the prescribed surface portion.
 7. A lens grinding lap as set forth in claim 4 wherein said cap member is of a non-ferrous material.
 8. A lens grinding lap as set forth in claim 4 wherein said cap member further includes an annular channel about said rim and said body member further includes a rim adjacent said annular channel and adapted to be received within said last named channel. 